Open position for a postdoctoral researcher to Investigating the mechanisms shaping the adaptation of the phytopathogenic bacterium Xylella fastidiosa to its host environments:

A two-year position for a postdoctoral researcher is open at the IRHS (Research Institute on Horticulture and Seeds) in Angers, France. The position will be part of the EU-funded project “Bexyl – Beyond Xylella, Integrated Management Strategies for Mitigating Xylella fastidiosa impact in Europe”. This project involves 30 partner institutions from 14 countries, providing extensive opportunities for international collaborations.

Xylella fastidiosa is a phytopathogenic bacterium with a strong adaptive capacity, as evidenced by its genetic diversity and wide range of host plants. It specifically colonizes the xylem of plants and is transmitted by hemipteran insects that feed on xylem sap. Originally from the Americas, the bacterium is now present in several European countries due to accidental introductions of infected plant material. These introductions have caused the emergence of new diseases in Europe (e.g. the “Olive quick decline syndrome” in Italy or Almond Leaf Scorch in Spain).

The aim of this project is to investigate the mechanisms shaping the adaptation of this pathogen to its host plants, including the host-associated microbiota. This is particularly relevant in its new areas of distribution, where X. fastidiosa may establish new pathogen-plant relationships compared to its native area, effectively increasing its host range.

This has been the case in the south of France, where multiple strains have been introduced decades ago: the bacterium infects mostly ornamental plants and native plants of the Mediterranean shrubland, providing a unique opportunity to investigate pathogen adaption to new host plants in a diverse landscape. Indeed, it has been hypothesized that a diverse plant community would select for more generalist (and potentially less virulent) genotypes and maintain a higher genetic diversity in the pathogen population compared to crop monocultures.

Within this project, the postdoctoral researcher can investigate several research avenues, depending on interest:

* Investigate the genetic basis underlying host plant adaptation in X. fastidiosa. The availability of high quality genomes from a large panel of strains isolated in France allows the identification of genes under selection that might be involved in pathogen-plant interactions. The impact of these candidate genes on pathogenicity can then be functionally validated in planta, benefitting from the advantage that X. fastidiosa mutants are produced very easily.

* Compare the host range, infection dynamics and pathogenicity of introduced and alien strains on typical Mediterranean host plants as well as classic X. fastidiosa-pathosystems (e.g. grapevine)

* Investigate interactions between X. fastidiosa and the host-associated microbiota, which represents an integral part of the host environment encountered by the bacterium. Whereas investigations regarding the bacterial and fungal communities present in the plant xylem will be performed as part of a concomitant PhD project, the postdoctoral researcher could focus on the viral community, including bacteriophages.

Candidate requirements: We are looking for a highly motivated early career researcher with a PhD in microbiology microbial ecology or microbial genomics and a keen interest in host-microbe interactions. The successful candidate should therefore have good experience in the lab (microbiology, molecular biology, genetics) as well as with bioinformatics (genome analysis).

Additional work experience or knowledge about plants as host organisms would be an advantage. The candidate must be fluent in English (speaking and writing) and have good organisational and communication skills.

Research environment: The project will be supervised by Marie-Agnès Jacques and Jessica Dittmer. The postdoctoral researcher will integrate the Emersys research group at the IRHS (Research Institute on Horticulture and Seeds).

The IRHS is a joint research unit (260 staff) affiliated with the French National Research Institute for Agriculture, Food and Environment (INRAE), the University of Angers and the Institut Agro, a French higher education institute in Agriculture, Food, Horticulture and Landscape Sciences. The IRHS has very strong expertise in plant pathology, plant physiology, microbial ecology and plant phenotyping.

It has extensive research facilities, including 9000 m2 greenhouse facilities, a high-throughput plant phenotyping platform, an in-house DNA sequencing facility and core servers for data storage and analysis. It also houses the French Collection of Plant-associated Bacteria (CIRM-CFBP) as well as S3 laboratories to work with GMO and quarantine organisms.

Angers is a vibrant middle-sized city in western France, about 300 km southwest of Paris and close to the Atlantic Ocean. It is located just north of the Loire Valley, a UNESCO World Heritage site famous for its landscape, historic towns and castles. Angers enjoys a rich cultural life, thanks to numerous higher education institutions and museums. Moreover, the city is renowned for its specialization in the plant sector (Végépolys is Europe’s leading horticultural competitiveness cluster).

Benefits: The gross salary will be about 3000 €/month, depending on previous work experience, plus additional benefits. How to apply For informal inquiries, please contact Marie-Agnès Jacques ( and Jessica Dittmer (

To apply: Applications should include a CV, a motivation letter (in English or in French), a complete publication list and the names and email addresses of two referees. Please send your application as a single pdf to and with ‘’Application Postdoc Xylella’’ in the subject line.

Application deadline: 21 July 2023
Desired start date: November 2023

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